Isa Ibrahim was a troublemaker at my school, but drugs and Islamism made him a terrorist

The blank stare was unrecognisable when Isa Ibrahim appeared on last night's News at Ten. But it was definitely him – Andy, one of the most difficult boys I came across during my time in education. Now a young man, he had become "Isa", sentenced to ten years in jail after police discovered his plans to suicide bomb a Bristol shopping centre.

When I knew Ibrahim – before his conversion to Islam and his change of name – he was a troublemaker, but certainly no terrorist. He was a couple of years below me at Downside, a Catholic school near Bath which was all boys until 2005. Even as public schools go, it was notably tough – many more of my schoolmates ended up in the Army than went to Oxbridge.

Ibrahim didn’t last long. Yesterday, the judge noted his "craving for attention". It reminded me of one of my English classes. We were studying Heart of Darkness when loud shouting was heard from the next-door classroom. "Go to the detention room, you’re an absolute ass!", a usually calm teacher bellowed. As my class looked up in surprise, Ibrahim loped past looking vaguely bored.

It would be wrong to suggest Ibrahim was bullied at Downside. But he really did crave attention, even if it was evidently self-injuring. He never bothered to be cheeky to me; instead, he would antagonise and insult front row forwards in the 1st XV rugby team. The more pain, the better.

To those in his year-group, however, he seemed different. I wrote a short blog post about Ibrahim last year, soon after his arrest. A comment rapidly appeared from a friend. "He was definitely not a loner, so it’s probably best to get the facts right before you write such ****," he wrote angrily.

There were times when Ibrahim wasn’t such a pain. I remember noticing his incredibly speedy touch-typing in the school computer room. I’d never seen anyone type as fast, and I praised him for it. His response was surprising: he offered to type up my handwritten essays in case I would like to redraft them on a computer. I declined, sensing his neediness.

So how did a difficult boy become a young man so filled with hatred that he wished to blow himself up in a crowded shopping centre? In short, how did Andy transform into "Isa", staring out at me from the Ten O’Clock News? The truth is, we may never know. It could have been the various schools he was sent away to. Or that his mixed-race parentage caused a crisis of identity.

More likely, though, it was an addiction to drugs that made Ibrahim’s life disintegrate. He started on cannabis at a young age, and became lazy with school work. So he got in trouble with his teachers – and maybe his parents – which led to a resentment of figures of authority. The drug habits worsened, and he became addicted to heroin and cocaine.

Eventually, radical Islam offered Ibrahim a way out. It gave him a sense of identity. It granted him a feeling of imagined acceptance in a community of outcasts. It even helped him to overcome his drug addiction. How tragic and utterly terrifying, then, that it also inspired his lonely vision of suicide and mass murder.